DE102016122513B3 - Method for dismantling a steam generator or heat exchanger, in particular a steam generator or heat exchanger of a nuclear power plant - Google Patents

Abstract

The invention relates to a method for dismantling a steam generator (10) or heat exchanger, in particular a steam generator (10) or heat exchanger of a nuclear power plant, the steam generator (10) or heat exchanger having a plurality of contaminated on its inside pipe primary circuit tubes (11), wherein one or more of the tubes (11) are closed at both tube ends (12) with a stopper (13). The method according to the invention comprises the following steps: a) opening one or both ends (12) of each sealed tube (11) by inserting an opening (14) in the respective plug (13) or by removing the respective plug (13); b) introducing a viscous and in the pipe (11) curing polymer (24) in the first or closed and now open tubes (11), wherein the polymer (24) the pipe (11) at least in the region of the pipe ends (12) fills the entire pipe cross-section and fixed in the filled section contaminations in the pipe (11); c) separating the polymer (24) provided tubes (11) after curing of the polymer (24), wherein the separated tubes (11) are closed by the cured polymer (24), d) sorting out with the polymer (24) provided and separated pipes (11).

Description

The invention relates to a method for dismantling a steam generator or heat exchanger, in particular a steam generator or heat exchanger of a nuclear power plant.

Such steam generators or heat exchangers have a multiplicity of primary circulation pipes contaminated on their inner side of the pipe, one or more of the pipes being closed at both pipe ends with a stopper.

In the nuclear reactor of a nuclear power plant is the reactor core, which consists of fuel elements in which nuclear energy is released by controlled nuclear fission and radioactive decay and converted into heat. With this heat, a coolant is heated, which is pumped through the reactor, thereby removing the energy from the reactor. The coolant is then fed to a steam generator, whereby the turbines of the power plant are driven by the generated steam.

The steam generator transfers the heat of the reactor coolant to the water-steam circuit. As shell-and-tube heat exchangers, these produce fresh steam from feedwater to drive the turbines.

The collection chamber is connected to the main coolant lines of the reactor cooling system via inlet and outlet ports. From the collection chamber, the reactor coolant flows through the tubes to the discharge chamber with heat release, from where it is fed to the main coolant pump.

The tube bundle is connected to the tubesheet of the steam generator. The tubes of a steam generator can be up to 20 meters long. The incoming feedwater flows in the natural circulation in the tube bundle upwards. In the steam dome above the tube bundle, the residual vapor moisture is separated before the dried steam is discharged via the outlet nozzle.

The inner surfaces of the tubes of steam generators in nuclear power plants are contaminated during operation of the plant. Regular inspections of the pipes ensure their integrity. If it should be determined during a test that damage, such as a reduction in wall thickness, is present, this pipe is for safety's sake closed on both sides, at the inlet end and at the outlet end, with plugs in the tube bottom area. This has the consequence that also the surface contamination is included.

When dismantling the steam generator, the tubes are decontaminated in a preliminary step, for example by mechanical or chemical processes. Since the tubes previously closed by the plugs are inaccessible to such decontamination, there is the problem that these tubes can not be further processed without additional steps or returned to dismantling.

It is therefore an object of the invention to provide a method by which it is avoided that contaminants that are present on the inner surfaces of the tubes when disassembling the steam generator or heat exchanger can not escape from the pipes.

This object is achieved by a method for dismantling a steam generator or heat exchanger with the features according to claim 1. Advantageous embodiments and further developments are specified in the respective dependent claims.

• a) Öffnen eines oder beider Enden jedes verschlossenen Rohres durch Einbringen einer Öffnung in den jeweiligen Stopfen oder durch Entfernen des jeweiligen Stopfens;
• b) Einbringen eines viskosen und im Rohr aushärtenden Polymers in das oder die zunächst verschlossenen und nunmehr geöffneten Rohre, wobei das Polymer das Rohr zumindest im Bereich der Rohrenden über den gesamten Rohrquerschnitt ausfüllt und im ausgefüllten Abschnitt Kontaminationen im Rohr fixiert;
• c) Abtrennen der mit Polymer versehenen Rohre nach dem Aushärten des Polymers, wobei die abgetrennten Rohre durch das ausgehärtete Polymer verschlossen sind,
• d) Aussortieren der mit dem Polymer versehenen und abgetrennten Rohre.

The method according to the invention comprises the following steps:

• a) opening one or both ends of each sealed tube by inserting an opening in the respective plug or removing the respective plug;
• b) introducing a viscous and curing in the tube polymer in the first or closed and now open tubes, wherein the polymer fills the tube at least in the region of the tube ends over the entire pipe cross-section and fixed in the filled section contaminations in the pipe;
• c) separating the polymerized tubes after the curing of the polymer, wherein the severed tubes are closed by the cured polymer,
• d) sorting out the tubes provided with the polymer and separated.

By introducing a polymer which cures in the tubes, the loose contamination is bound in the tube and can not escape when the tube is separated.

It has become widely accepted that the decommissioning of nuclear power plants as the last step before shutdown nor a so-called "full system decontamination" is performed. Since radioactive waste is very expensive, care must be taken that as little "high-level radioactive waste" is produced. The non-plugged open tubes and the closed tube filled with the polymer have different waste categories so that the closed tubes filled with the polymer are sorted out and be disposed of separately from the non-plugged open tubes.

The advantages of the invention are, in particular, that any chemical or mechanical treatment of the contaminated tubes can be avoided by the method according to the invention. Such treatment of the pipes always carries the risk due to the pre-damage of the pipes that the pipes will be broken, leading to contamination on the secondary side. Such a carry-over of contamination must be avoided in any case, since the secondary side is basically contamination-free.

Furthermore, it is an advantage of the invention that the method is on the one hand much cheaper than known, alternative methods and on the other hand brings a very high level of security.

According to an advantageous development of the invention, it is provided that a crosslinking polymer, in particular a polyaddition-crosslinking polymer, for example consisting of or comprising silicone and / or polyurethane and / or epoxy resin, is used.

According to one embodiment of the invention can be provided that the tube interior is completely filled with the polymer. Furthermore, according to an alternative embodiment variant of the invention, provision may be made for the tube interior to be filled with the polymer in the region of the two tube ends, for example from the tube end to 0.5 meters beyond the tubesheet.

By "complete" it can be understood that the complete interior of the tube is filled from one tube end to the other with the polymer. In other words: There should be no cavities or free areas left in the pipe. By "in the region of the tube ends" it can be understood that the polymer extends into the tube after insertion at both ends from the tube end, for example, up to 0.5 meters beyond the tubesheet. In other words, a void or free area remains between the two filled areas.

It can be provided that the polymer is introduced by means of one or more lines, wherein a line is introduced through an open pipe end or a line through each open pipe end of a pipe in the pipe. The conduit may be, for example, a hose or a flexible pipe.

In order to supply the line or lines to the pipe end or ends, these can be fed via the manholes or the loop lines to the steam generator or heat exchanger.

Such lines should have the largest possible inner diameter, so that the frictional resistance during the pressing of the still low-viscosity polymer at this time is as low as possible.

The polymer is introduced in particular by means of pressure, wherein the pressure is preferably generated by a pressure unit which is connected to the polymer mixer. The pressure applied to the unit can vary between 1 bar overpressure and 150 bar overpressure. This depends on the circumstances, such as diameter and / or length of the pipe and the pipe.

According to one embodiment, the tubes are U-shaped tubes whose two ends terminate in a tubesheet, wherein a conduit inserted through one of the open tube ends, then passed to the apex of the U-shaped tube and then pressed the polymer through the conduit into the tube is withdrawn, wherein the line is withdrawn from the tube during the pressing of the polymer until the interior of the corresponding half of the tube is filled with polymer.

According to an alternative embodiment, the tubes are U-shaped tubes whose two ends terminate in a tube sheet, wherein a line inserted through one of the open tube ends in the tube, then about 0.5 meters out over the tubesheet out into the tube and then the polymer is forced through the conduit into the tube, the conduit being withdrawn from the tube upon injection of the polymer until the corresponding portion of the tube is filled with polymer.

In both embodiments, the second half or the second portion of the tube can be filled by the second open end of the tube in an analogous manner with polymer at the same time or in the wake of pressing the polymer into the corresponding half or in the corresponding portion of the U-shaped tube.

According to a development of the invention, it is provided that all tubes not sealed with plugs are decontaminated before opening the sealed tubes, in particular with mechanical or chemical cleaning methods, for example by abrasive methods, such as blasting methods, or by rinsing methods with solvents.

The openings may be made by drilling, in particular by means of a two-stage drilling process, placed in the plugs to prevent loose parts. An introduction by means of milling or erosion or other suitable methods is possible. The openings may for example have a minimum diameter of about 5mm. The maximum diameter preferably corresponds approximately to the inner diameter of the tube, ie the plug is completely removed. The inner diameters of the tubes can have a diameter of approximately 10 to 20 mm.

When separating the tubes provided with the polymer, it is also preferable to separate the open-tube not provided with plugs and then to sort out the tubes provided with the polymer.

A preferred and expedient development of the invention provides that the tubes provided with polymer and / or the non-plugged, open tubes are separated directly on or near the tube plate or at the level of the tube plate, in particular by sawing, wherein along a provided Dividing line is separated, which is preferably provided perpendicular to the vertically standing tubes. Alternatively, it is also possible to separate the pipes in the lying state. The dividing line can for example be provided directly on or near the tube bottom. However, the dividing line may also be provided through the tubesheet.

Preferably, the tubes completely filled with polymer, preferably after separation, are segmented into several pieces, the segmentation being carried out by means of cutting and / or sawing and / or thermal separation processes. Such a segmentation facilitates the further treatment or transport of the tubes, since they are very long in the non-segmented state with up to 20 meters.

It can be provided that the separated and sorted provided with the polymer pipes are treated and / or disposed of as radioactive waste.

Alternatively or additionally, it can be provided that the unopened open tubes after disassembly are treated and / or disposed of as less radioactively contaminated waste or non-radioactively contaminated waste.

The separated and sorted polymer-provided pipes as well as the non-plugged open pipes can be assigned to different waste categories and disposed of separately.

The invention will be explained below with regard to further features and advantages with reference to the description of embodiments and with reference to the accompanying drawings. 1 shows a simplified, schematic representation of a steam generator 10 in which the inventive method for dismantling a steam generator 10 can be carried out. For a better overview, only an enlarged primary circuit pipe is shown in the steam generator 11 shown. In general, however, a steam generator includes a plurality of tubes 11 , for example, several thousand such pipes 11 ,

1 shows a steam generator 10 a nuclear power plant (not shown), the steam generator 10 a plurality of contaminated on its inside pipe primary circuit pipes 11 having ( 1 exemplarily shows only such a tube 11 ), one or more of the tubes 11 at both ends of the pipe 12 with a stopper 13 were closed. In the ground state in which the process starts, the pipe ends are 12 still with a stopper 13 locked.

In the method according to the invention is first one or both ends 12 every sealed pipe 11 by introducing an opening 14 in the respective stopper 13 or by removing the respective plug 13 open. 1 shows a pipe 11 in which in both ends 12 are open, at the right-hand end 12 by introducing an opening 14 in the stopper 13 , at the left end 12 by removing the plug 13 ,

The openings 14 are preferably by drilling, in particular by means of a two-stage drilling process, in the plug 13 introduced to prevent loose parts. However, instead of drilling, milling or eroding methods are also possible.

All are not preferred with stopper 13 closed pipes 11 before opening the sealed tubes 11 with mechanical or chemical cleaning methods, for example by abrasive methods, such as blasting method, or by rinsing with solvents, decontaminated.

After opening one or both ends 12 every sealed pipe 11 becomes a viscous and in the pipe 11 curing polymer 24 in the one or the first closed and now open pipes 11 brought in. The polymer 24 fills the tube 11 at least in the area of the pipe ends 12 over the entire pipe cross section and fixed in the filled section contaminations in the pipe 11 ,

As the polymer, a polyaddition-crosslinking polymer 24 For example, consisting of or comprising silicone and / or polyurethane and / or epoxy resin used.

In the following, two variants for introducing the polymer are shown:
According to the first variant, the pipe interior 16 completely with the polymer 24 filled. Here, the polymer 24 by means of a hose designed as a hose 15 introduced, with the hose 15 through an open pipe end 12 is introduced.

To the hose 15 the pipe end 12 This can pass through the manhole 20 and / or the loop lines 21 the steam generator 10 be supplied. The polymer 24 is introduced in particular by means of pressure, wherein the pressure through a pressure unit 23 , which with the polymer mixer 22 connected is generated.

The pipes 11 of the steam generator 10 are U-shaped tubes 11 whose two ends 12 in a tube sheet 17 end up. The hose 15 is through one of the open pipe ends 12 , in 1 through the right end of the pipe 12 introduced and then to the vertex 18 of the U-shaped tube 11 guided. Subsequently, the polymer 24 through the hose 15 in the pipe 11 pressed, with the hose 15 during the pressing of the polymer 24 out of the pipe 11 is withdrawn until the interior 16 the corresponding half of the pipe 11 with polymer 24 is filled. 1 shows the beginning of the press-fitting process. It is already part of the pipe 11 provided with polymer, and the hose 15 is already a piece from the tube 11 withdrawn.

At the same time or in the aftermath, in 1 in the aftermath, for pressing in the polymer 24 in the corresponding half of the U-shaped tube becomes the second half of the tube 11 through the second open pipe end 12 in an analogous manner with polymer 24 filled.

According to the second, in 1 not shown, variant is the pipe interior 16 in the area of the two pipe ends 12 For example, over a length of about 0.5 meters, measured from the top of the tubesheet, with the polymer 24 filled. This is polymer 24 by means of two hoses 15 introduced, each with a hose 15 by one open pipe end 12 a pipe 11 in the pipe 11 is introduced.

The pipes 11 are U-shaped tubes 11 whose two ends 12 in a tube sheet 17 ending, being a hose 15 through one of the open pipe ends 12 in the pipe 11 and then about 0.5 meters, measured from the upper end of the tubesheet, into the tube 11 to be led. Subsequently, the polymer 24 through the hose 15 in the pipe 11 pressed, with the hose 15 during the pressing of the polymer 24 out of the pipe 11 is withdrawn until the corresponding section of the pipe 11 with polymer 24 is filled.

At the same time or in the wake of pressing in the polymer 24 in the corresponding section of the U-shaped tube 11 becomes the second section of the pipe 11 through the second open pipe end 12 in an analogous manner with polymer 24 filled.

After curing of the polymer 24 Be the one with polymer 24 provided pipes 11 separated. The severed pipes 11 are at this time by the cured polymer 24 locked.

When separating with the polymer 24 provided pipes 11 are also preferred also not with plugs 13 provided open tubes 11 separated.

The with polymer 24 provided pipes 11 as well as those not with plugs 13 provided open tubes 11 be directly on or near the tube bottom 17 separated by sawing, being separated along an intended dividing line A, which is perpendicular to the vertically standing tubes 11 is provided. Alternatively, the dividing line may also be provided through the tubesheet (not shown).

The with the polymer 24 provided and severed pipes 11 are then sorted out.

The complete with polymer 24 filled pipes 11 are segmented after separation into several pieces, wherein the segmentation is performed by means of sawing or other separation methods.

The separated and sorted out with the polymer 24 provided pipes 11 are treated and disposed of as radioactive waste. Not with plugs 13 provided open tubes 11 are treated and disposed of as less radioactive waste or non-radioactive waste after dismantling.

LIST OF REFERENCE NUMBERS

10

 steam generator

11

 pipe

12

 pipe end

13

 Plug

14

 Opening in the stopper

15

 tube

16

 inner space

17

 tube sheet

18

 vertex

19

 hand hole

20

 manhole

21

 Loop line

22

 polymer mixers

23

 pressure unit

24

 polymer

A

 parting line

Claims (13)

Method for dismantling a steam generator ( 10 ) or heat exchanger, in particular a steam generator ( 10 ) or heat exchanger of a nuclear power plant, wherein the steam generator ( 10 ) or heat exchanger a plurality of contaminated on its inside pipe primary circuit tubes ( 11 ), wherein one or more of the tubes ( 11 ) at both pipe ends ( 12 ) with a stopper ( 13 ), comprising the following steps: a) opening one or both ends ( 12 ) of each sealed tube ( 11 ) by introducing an opening ( 14 ) in the respective plug ( 13 ) or by removing the respective plug ( 13 ); b) introducing a viscous and in the pipe ( 11 ) curing polymer ( 24 ) into the initially closed and now opened tubes ( 11 ), wherein the polymer ( 24 ) the pipe ( 11 ) at least in the region of the pipe ends ( 12 ) over the entire pipe cross section and in the filled section contaminations in the pipe ( 11 ) fixed; c) separating the polymer ( 24 ) ( 11 ) after curing of the polymer ( 24 ), the separated tubes ( 11 ) by the cured polymer ( 24 ), d) sorting out with the polymer ( 24 ) and separated tubes ( 11 ). Process according to Claim 1, characterized in that a crosslinking polymer ( 24 ), in particular a polyaddition-crosslinking polymer ( 24 ), for example consisting of or comprising silicone and / or polyurethane and / or epoxy resin, is used. A method according to claim 1 or 2, characterized in that the tube interior ( 16 ) completely with the polymer ( 24 ), or that the interior of the pipe ( 16 ) in the region of the two pipe ends ( 12 ), for example, from the pipe end to 0.5 meters above a tube sheet ( 17 ), with the polymer ( 24 ) is filled. Method according to one of the preceding claims, characterized in that the polymer ( 24 ) by means of one or more lines ( 15 ) is introduced, wherein a line ( 15 ) through an open pipe end ( 12 ) or one line each ( 15 ) by one open pipe end ( 12 ) of a pipe ( 11 ) in the pipe ( 11 ) is introduced. Method according to claim 4, characterized in that the tubes ( 11 ) U-shaped tubes ( 11 ) whose two ends ( 12 ) in a tubesheet ( 17 ), whereby one line ( 15 ) through one of the open pipe ends ( 12 ), then to the vertex ( 18 ) of the U-shaped tube ( 11 ) and then the polymer ( 24 ) through the line ( 15 ) in the pipe ( 11 ) is pressed, the line ( 15 ) when pressing in the polymer ( 24 ) out of the pipe ( 11 ) is withdrawn until the interior ( 16 ) of the corresponding half of the tube ( 11 ) with polymer ( 24 ) is filled. Method according to claim 4, characterized in that the tubes ( 11 ) U-shaped tubes ( 11 ) whose two ends ( 12 ) in a tubesheet ( 17 ), whereby one line ( 15 ) through one of the open pipe ends ( 12 ) in the pipe ( 11 ), then about 0.5 meters beyond the tubesheet into the tube ( 11 ) and then the polymer ( 24 ) through the line ( 15 ) in the pipe ( 11 ) is pressed, the line ( 15 ) when pressing in the polymer ( 24 ) out of the pipe ( 11 ) is withdrawn until the corresponding section of the tube ( 11 ) with polymer ( 24 ) is filled. A method according to claim 5 or 6, characterized in that simultaneously or subsequently to the pressing of the polymer ( 24 ) into the corresponding half or section of the U-shaped tube ( 11 ) the second half or the second section of the tube ( 11 ) through the second open pipe end ( 12 ) in an analogous manner with polymer ( 24 ) is filled. Method according to one of the preceding claims, characterized in that all are not filled with plugs ( 13 ) sealed pipes ( 11 ) before opening the sealed tubes ( 11 ), in particular with mechanical or chemical cleaning methods, for example by abrasive methods, such as blasting methods, or by rinsing with solvents, decontaminated. Method according to one of the preceding claims, characterized in that the openings ( 14 ) by drilling, in particular by means of a two-stage drilling process, in the plug ( 13 ) are introduced to prevent loose parts. Method according to one of the preceding claims, characterized in that when separating with the polymer ( 24 ) ( 11 ) also not with plugs ( 13 ) provided open pipes ( 11 ) and then the polymer ( 24 ) ( 11 ) are sorted out. Method according to one of the preceding claims 5-10, characterized in that the with polymer ( 24 ) ( 11 ) and / or not with plugs ( 13 ) provided with open tubes ( 11 ) directly on or near the tubesheet ( 17 ) or at the level of the tube bottom ( 17 ), in particular be separated by sawing, being separated along an intended dividing line (A), which is preferably perpendicular to the vertically standing pipes ( 11 ) is provided. Method according to claim 3, first alternative, characterized in that the completely with polymer ( 24 ) filled tubes ( 11 ), preferably after separation, are segmented into a plurality of pieces, the segmentation being carried out by means of cutting and / or sawing and / or thermal separation processes. Method according to one of the preceding claims, characterized in that the separated and sorted out with the polymer ( 24 ) ( 11 ) are treated and / or disposed of as radioactive waste and / or that are not filled with plugs ( 13 ) provided with open tubes ( 11 ) are treated and / or disposed of as less radioactively contaminated waste or non-radioactively contaminated waste after dismantling.

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